A ball that turns round

Challenge 8 of 12

A CYAN ball 80 wide at 180 down, starting at 40 across and moving 8 to the right every frame, on BLACK. When its across number goes over 340, turn the speed into its own negative so it comes back.

Write it.

Your code JavaScript

Write it.

Console print() output

0 / 40 frames · 400×400

Target

Yours

Yours over Target — ghosted shapes are in the target but missing from yours

Results

Press Run to check your code

Penalties: none this run

Report this challenge

Lesson Code it yourself

The editor is empty. There is no code to fill in, no highlighted holes, and nothing to read except the description at the top of the page.

The row of buttons above the editor is the block palette. Each one drops a ready-made piece of code in at the cursor — everyFrame, a for loop already counting 0 to 4, an if with a working question in it, an else. Click one, then edit the numbers and names inside it until it says what you want.

The if button gives you this:

if (frameNumber > 10) {

}

which is a real question about a real number, so it runs as it stands. Change what it asks about and what goes inside it.

Everything in this topic asks its question about something that CHANGES. That is not decoration. A question about a number that never moves always gives the same answer, so it may as well not be there — and you would be quicker drawing the picture by hand. Put the if inside a loop and the counter changes it on every turn. Put it inside everyFrame and time changes it.

Read each description as a list of instructions in order. It tells you how many shapes there are, where the first one goes, how far apart they are, what the question asks and what each answer does. Everything you need is in it, and nothing that is not.

There is no readout along the bottom in this topic. Turn the grid on if you want to check where your shapes have actually landed, and press Try to watch an animation run past the frames the marking uses.

Nothing here is new. It is the same eight topics, with the page left blank.